Self-locking folding boxes



June 3, 1958 c, STENGER 2,837,261

SELF-LOCKING FOLDING BOXES Filed A ril 1, 1955 4 Sheets-Sheet 1 v INVENTOR. W C. St 9 n4 A TTORNEY R. C. STENGER SELF-LOCKING FOLDING BOXES June 3, 1958 4 Sheets- Sheet 2 Filed April 1, 1955 INVENTOR.

4; ATTORNEY June 3, 1958 (3, N R 2,837,261

SELF-LOCKING FOLDING BOXES Filed April 1, 1955 4 Shets-Sheet 3 INVENTOR.

M C. 5& BY 3 E L W '5. A4. ATTORNEY R. c. STENGER SELF-LOCKING FOLDING BOXES June 3, 1958 4 Sheets-Sheet 4 Filed April 1, 1955 INVENTOR. M C 5 United States Patent SELF-LOCKENG FOLDING BOXES Richard C. Stenger, San Carlos, Calif., assignor to Baljak Corporation, Wilmington, DeL, a corporation of Dela ware Application April 1, 1955, Serial No. 498,510

'8 Claims. (Cl. Z2 935) This invention relates to improvement in cartons, trays or other structures made from blanks of cardboard, paperboard, or other suitable foldable sheet material, hereinafter collectively referred to as boxes or folding boxes. 1

More particularly the invention applies to gluelessly as sembled folding boxes in which the box corners are locked by engagement of cut edges of overlapping or interlaced flaps and panels at, or adjacent, the corners of the box structure.

This invention provides, specifically, an improvement over a basic form of box corner construction disclosed in my co-pending application, Serial No. 396,123, filed December 4, 1953, now Patent No. 2,785,845. The corner construction disclosed and claimed in the aforementioned application is capable of being assembled and locked at high production speeds by a box assembly and locking mechanism of the plunger and die type. The disclosed corner construction lends itself admirably to the construction of lined folding boxes, such as frozen food boxes in which a liner provides liquid tightness. The corner construction disclosed in the aforementioned patent application insures automatic folding of the liner at the box corners into neat gusset folds and, in addition, permits use of a locking mechanism which does not reach through, or penetrate, the box walls as a result of which the liner would be injured and the liquid proofness destroyed.

The present invention provides improvements which guard the box corners against accidental unlocking of the interengaging cut edges in the several flaps or panels.

Accidental disengagement, may result from anynumber of causes, nearly all of which may be characterized by the fact that they tend to distort the box corners in such a way that its individual flaps or vpanels are moved beyond the position in which the box corner is accurately squared. This result may be produced by a malfunctioning of the box assembly mechanism, by the box conveyor which then moves the assembled empty box to a filling machine, by actions of the filling machine, by actions of the closingmachine or by actions of the overwrapping machine, if such a machine is employed.

The construction disclosed in the aforementioned patent application includes a guard against accidental disengagemerit in the form of an abutment between panels and edges, for example by letting a box panel rest against an. edge formed by the folding of an internal corner flap. This arrangement is quite satisfactory unless there. are influences which would tend to permit the creases of the box blank, which lie in register in the assembled, corner, to slide or curl a certain distance beyond their proper position.

According to the present invention this is avoided by providing a positive stop for the lock flap containing the critical locking cuts or edges on which the engagement of the corner lock depends.

It hasheretofore been proposed to maintain the lock flap in overlapping position on the outside. of awall panel by providing an internal cut in the wall panel. This in- "ice ternal cut produces a tongue which, in turn, overlies the lock flap.

According to the presentinvention this internal tongue is modified and given a multiple function or purpose, as a result of which the tongue not only overlies the corner flap but also provides a positive stop limiting the movement of thelock flap in such a way that it cannot move beyond the position in which the corner is accurately squared. The invention also provides certain simplifications in the shape of the inter-engaginglocking cuts.

These and various other features, objects and advantages of the invention will appear more fullyfrom the detailed description which follows, accompanied by drawings showing, for the purpose of illustration, a preferred.

out in the claims appended hereto, the invention itself and the manner in which it may be carried out, may be better understood by referring to the following description taken in connection with the accompanying drawings;

forming a part of it in which:

Fig. l is a plan view of a flat box blank embodying the invention, the inside surface of the blank facing the ob Fig. 2 is a perspective view of the blank of Fig. 1 com-- bined with a liner;

Figs. 3, 4 and 5 illustrate, in perspective views, successive stages of the assembly;

Fig. 6 is a perspective view, on an enlarged scale, of a: folded box corner prior to completion of the lock;

Fig. 7 is a perspective view of the box corner of Fig. 6' after completion of the lock;

Fig. 8 is a perspective view of the erected box ready for filling; and

Fig. 9 is a perspective view of the filled and closed box.

In the following description and in the claims, various structural details will be identified by specific names for convenience. The names, however, are intended to be generic in their application. Corresponding reference characters refer to corresponding parts in the several figures of the drawings.

In the drawings accompanying, and forming part of, this specification, certain specific disclosure of the invention is made for the purpose of explanation of broader aspects of the invention, but it is understood that the details may be modified in various respects without departure from the principles of the invention and that the invention may be applied to other! structures than the one shown. 1

The blank A may be cut and scored,- in multiple, from a large sheet or roll of paperboard or other suitable foldable material on an automatic cutting and creasing machine.

The blank A is traversed by several scored fold lines to provide a main or bottom panel 11 to which a front panel 12 and a back panel 13 are articulated along a front Corner flaps 28, 29, 30 and 31 ma'y be articulated to'the sidepanels 16 and 17 along:.cornerflapfold lines 32, 33, 34 and 35, respectively A top panel 36 is articulated to theback panel 15 along These corner fold lines are either 45 fitting into cuts 46 and 47 in the side panels 16 and 17, respectively. Similarly, the front tuck fiap 38 has a locking tab 48 fitting into a cut 49 in the front panel 12 and engages edge portions 50 and 1 of the cut with correspondingly oriented edge portions 52 and 53 of the tab 48. These cover locking details are in common use and do not form a part of the present invention.

The improved corner locks of the box blank comprise external cuts in the side wall panels and in the associated lock flaps. These cuts are moved into interlocking engagement after erection of the front, back and side panels of the box into upright position in regard to the bottom panel.

In the illustrated embodiment the construction of all four box corners is alike, and it will therefore be sufficient to describe one of the four external cuts 54, 55, 56 and 57 in the lock flaps 20, 21, 22 and 23, which are brought into engagementwith other external cuts 58, 59, 60 and 61 in the side panels 16 and 17, respectively.

At least one of the interengaging external cuts is of offset outline. In the illustrated blank the external cut 55 comprises an exterior portion 62, an intermediate portion 63 and an interior portion 64. The exterior portion 62 is offset relatively to the exterior portion 64, and the interior portion 64 may be straight and substantially vertical with respect to the front fold line on the bottom panel 11 of the erected box.

The corresponding external cut 59 in the side panel 17 comprises an interior portion 65 and an exterior portion 66. When the panels and flaps are in corner-forming position, as is also shown in Figure 6, the interior portion 65 of the cut 59 is in register with the interior portion 64 0f thecut 55.. This permits edges of the two outs to be brought into edge-to-edge engagement, as will later be described. As is best seen in Figure 6, the exterior portions of the two cuts are not in register, but are offset. The amount of the oifset is roughly equal to the extent of the intermediate portion 63 of cut 55.

The oifset is selected in accordance with the flexibility of the board. In the type of board more commonly used for frozen food packages, the offset may be of the order of 7432 Of an inch, or roughly 2%. mm.

For the purpose of locking, the corner assembly is flexed adjacent to the external portions 62 and 66 into the position shown in Figure 7. This will be described in greater detail further below. At thispoint it will suffice to say that the amount of ofiset should be such that the engagement shown in Figure 7 can be brought about without permanently creasing the board at the base of the tongue or projection 67 formed by the angularly disposed cuts 62 and 63.

Internal cuts 68, 69, 70and 71 of substantially L- shaped outline form internal tongues 72, 73, 74 and 75 in the side panels 16 and 17. The internal tongues point toward the respective box corners and anchor the lock flaps in flat, side panel overlying position when the box is set up. The internal cuts comprise substantially vertical portions 76, 77, 78 and 79 forming one leg of the L, and substantially horizontal portions 80, 81, 82 and 83 extending away from the box corner and forming the other leg of the L. The ends of the horizontal cut portions may be angled as shown at 84, 85, 86 and 87 and serve as a stop to arrest the end edges 88, 89, 90 and 91 of the lock flaps in the position in which the corners are fully squared and the interior portions of the locking cuts 54, 55, 56, 57 and 58, 59, 60 and 61 are in register.

A sheet 84 (Figure 2) of liquid impermeable liner material, for example, cellulose acetate, is adhesively secured to the blank\A along glue areas marked "11 in Figure 1.

The glue areas are so selected that the liner follows the folding motion of certain panels and flaps to which it is attached, and does not follow other flaps or blank portions to which it is not attached. The liner is substantially rectangular in outline and corresponds roughly to the size of the box blank A, not including the front tuck flap 38.

The blank A together with its liner 84 may be transformed into hollow box form either by hand, or preferably, by automatic box'machinery as disclosed in the copending application of Chester J. Pierce, Jr. and Thomas F. Burke, Serial No. 487,632, filed February 11, 1955. The machine operations, which may also be carried out by hand, are substantially as follows:

The side panels 16 and 17 are first folded towards upright position with respect to the bottom panel 11 along the side fold lines 18 and 19. The marginal portions, of the liner 84 which are adhesively secured to the side panel take part in this folding operation and cause a more or less indefinite crease to be formed in line with the fold lines 26, 42 and 27, 43 of the box blank. Preparatory to the folding of the side panels 16 and,17 ,the corner flaps 28, 29, 30 and 31 may be folded into substantially upright position. This is illustrated in Figure 3.

Figure 4 illustrates'the side panel 16 and 17 in substantially upright position. At about this time, the front panel 12 and the back panel 13 are folded about their respective fold lines 14 and 15 over the previously folded corner flaps 28, 29,30 and 31 and the lock flaps 20, 21, 22 and 23 are folded along their fold lines 24, 25, 26, and 27 to assume an angular position with respect to the front panel 12 and the back panel 13. Since the liner is adhesively secured to the corner flaps, the formation of corner gusset folds 92, 93, 94 and 95 of the liner was initiated by the folding of the corner flaps shown in Figure 3.

Figure 5 illustrates the position of the corner-forming flaps and panels at a point where the front panel 12 and theback panel 13 have moved approximately 45 degrees. At approximately this point the lock flaps 20, 21, 22 and 23 are guided to enter underneath the internal tongues 72, 73, 74 and 75.. For this purpose pressure may be exerted on these tongues from the inside. The deflection of the board at the point of application of the force as indicated by arrows 97 and 98. is slight and does not damage the liner. The flexing of the internal tongues opens the internal cuts sufiiciently for the lock flaps 20,21,22 and 23 to slide underneath until their end edges 88, 89, 90 and 91 are arrested by the ends 84, 85, 86 and 87 of the L-cuts 68,69, 70 and 71. In this position the corner is fully squared. The tongue 73 maintains the flap 21 in a position overlying the side panel 17.

In the condition illustrated in Figure 6, the box corners are ready for engagement of the looks as follows:

A force F is exerted in the direction and at the point indicatedby the: arrow 99 at the tongue or projection 67 formed by the oifset of the cut 55. At the same time the side panel 17 is supported on the inside along an area 100 between thecorner 25 proper and the end of the cut 62. This causes the tongue 67 to snap in back of the portion of the side panel which lies between thecut 66 and the fold line 33. The completed lock is shown in Figure 7'. The lock proper is formed by the interior portion 64 of the cut in the flap 21 and the interior portion 65 of the cut 59 in the side panel. This cut lies in register with the cut portion 64, but is not visible in Figure 7. However, it was previously explained that the two locking cuts, namely the cut 59 in the side panel and cut 55 in the lock flap are so laid out that the lower portions lie in register when the corner is square and the end edge 89 is arrested by the end 85 of the L-cut 69, so that, by flexing of the board, edges of the registering cuts can be brought into edge-to-edge engagement. This engagement locks the outwardly.

The exterior portion of the cuts, namely the portion 62 of the cut 55 andthe portion 66 of the cut 59, perform the function of a safety catch which keeps the edges of the lowerportions ofthe cuts in engagement.

The box corner is resistant to forces acting from the outside towards the inside by reason of the edge-to-panel engagement betweenthe side panel 17 and the front panel 12; More particularly, the side edge of the panel 17 represented by the fold line 33 rests against the interior panel surface of the front panel 12 adjacent the corner foldline 25; In addition the edge 89 is positively arrested by the end 85 of the cut'69.

In addition to being mechanically tight, the carton is fluid tight because of the formation of gussets at all four box corners, the gusset 93 being visible in Figures 6 and 7.

The locked carton is shown in Figure 8. It is ready for filling with merchandise and may then be closed in conventional manner by equally conventional closing machines. Figure -9 shows the closed carton in condition for overwrapping.

What is claimed .is: v

1. A folding box, particularly for use with a liner, the box being assembled from a single box blank comprising, a bottom panel; a front panel, and a back panel articulated to the bottom panel along a front fold line and a back fold line, respectively; side panels articulated to the'bottom panel along side fold lines; corner flaps articulated-to the ends of the side panels along corner flap fold lines; lock flaps articulated to the ends of the front and the back panels along lock flap fold lines which are substantially in coincidence with said corner fold lines, considering the set up box, said side panels having internal cuts in .them forming internal tongues in the side panels overlying said lock flaps in the assembled box, the internal cuts being of substantially inverted L-shape, the substantially vertical leg of the L being at a distance from the corner flap fold line less than the distance of the end edge of the lock flap from the lock flap fold line, the substantially horizontal leg of the L extending away from the corner and terminating at a point substantially in coinciprising a main box panel; a first wall panel articulated dence with said end edge of the lock flap in corner forming position thereby arresting the lock flap against movement beyond the position in which the corner is squared, said lock flap and said side panel being provided with an interlock including an external cut extending into the body of the side panel from its top edge and an external cut extending into the body of the lock flap from its top edge, said two external cuts having an interior portion remote from the respective top edge and an exterior portion adjacent the top edge, the interior portions of both cuts being in substantial coincidence when the box is set up, to permit engagement in the position in which the said end edge of the lock flap is arrested by the end of the horizontal leg of the L, the exterior portion of the side wall cut being at a greater distance from the respective flap fold line than the exterior portion of the lock flap cut, the exterior portion of the lock flap out being offset with regard to the interior portion of the lock flap cut, thereby forming a hook on the lock fiap pointing towards the lock flap fold line, the hook being sufficiently short to permit flexing of the stock without permanent creasing by pressure applied adjacent the hook and directed toward the inside of the box to snap the hook from a position overlying the end panel into a position underlying the end panel, whereby the far edge of the interior portion of the flap cut is flexed into engagement with the near edge of the interior portion of the side panel cut.

2. A construction as set forth in claim 1 in which the external cut in said side panel is a straight substantially vertical cut.

3. A corner construction for a folding box, particularly for use with a box liner overlying, and attached to, the inside surface of the box blank, the box corner comto said main panel along a first panel fold line; a second wall panel articulated to said main panel along a second panel fold line intersecting said first panel fold line at right angles; a corner flap articulated to said second panel along a corner flap fold line forming substantially a continuation of said first panel fold line, considering the blank in flat condition; a lock flap articulated to said first wall panel along a flap fold line forming substantially a continuation of said second panel fold line, considering the blank in flat condition; said second wall panel having an internal cut in it forming an internal tongue in said second panel overlying said lock flap in the assembled corner, the internal out being of substantially inverted L- shape, the substantially vertical leg of the L being at a'distance from the corner flap fold line less than the distance of the end edge of the lock flap from the lock flap fold line, the substantially horizontal leg of the L extending away fro-m the corner and terminating at a point substantially in coincidence with said end edge of the lock flap in corner forming position, thereby arresting the lock flap against movement beyond the position in which the corner is squared, said lock flap and said second panel being provided with an interlock including a first external cut extending into said lock flap from its top edge, said second wall panel having a second external cut extending into it from its top edge, each of said external cuts comprising an exterior portion adjacent the respective top edge and an interior portion remote from the top edge, the interior portions of both external cuts being in coincidence in the assembled corner, the exterior portions of said external cuts being out of coincidence by reason of the first cut meeting the top edge at a point closer to said lock flap fold line than the distance from the corner flap fold line to the point of entry of said second cut into the top edge of the second wall panel, the top portion of the lock flap on the far side of the first cut being flexible from a position overlying said second wall panel into a position underlying the near top portion of the second wall panel in the assembled corner, in which position the interior portions of the two cuts are in e'dge-to-edge engagement.

4. A corner construction for a folding box, particularly for use with a liner blank overlying, and attached to, the inside surface of the box blank, the box corner comprising a main box panel; a first wall panel articulated to said main panel along a first panel fold line; a second wall panel articulated to said main panel along a second panel fold line intersecting said first panel fold line at right angles; a corner flap articulated to said second panel along a corner flap fold line forming substantially a continuation of said first panel fold line, considering the blank in fiat condition; a lock flap articulated to said first Wall panel along a flap fold line forming substantially a continuation of said second panel fold line, considering the blank in fiat condition; said second wall panel having an internal cut in it forming an internal tongue in said second panel overlying said lock flap in the asembled corner, the internal cut being of substantially inverted L-shape, the substantially vertical leg of the L being at a distance from the corner flap fold line less than the distance of the end edge of the lock flap from the lock flap fold line, the substantially horizontal leg of the L extending away from the corner and terminating at a point substantially in coincidence with said end edge of the lock flap in corner forming position, thereby arresting the lock flap against movement beyond the position in which the corner is squared, said lock flap and said second panel being provided with an interlock including a first external cut and a second external cut, one of said cuts extending into the lock flap from its top edge, the other external cut extending into said second Wall panels from its top edge, each of said external cuts comprising an exterior portion adjacent the respective top edge and an interior portion remote from the top edge, the interior portion of both external cutsbeing in coincidence in the assembled corner, the exterior portion of the said first cut being offset with respect to the interior portion of said first cut, the exterior portion of the external cut meeting the top edge of the lock flap at a point closer to the lock flap fold line than the distance from the corner flap fold line to the point of entry of the cut into the top edge of the second wall panel measured from the corner flap fold line, the top portion of the blank stock adjacent the ofiset cut portion forming a hook tip capable of being resiliently displaced by pressure directed against the second wall panel and the overlying lock flap past the exteriorportion of the other cut into locking position, in which position the interior portions of the two cuts are in locking engagement.

5. A corner construction as set forth in claim 4 in which'one of the external cuts is a substantially straight vertically extending cut and in which the interior portion of the other cut is likewise substantially straight and vertical with respect to said main box panel.

6. A corner construction for a folding box, particularly for a lined box in which a box liner blank overlies, and is' attached to, the inside surface of the box blank, the box corner comprising a main panel; a first wall panel articulated to said main panel along a first panel fold line; a second wall panel articulated to said main panel along a second panel fold line intersecting said first panel fold line at right angles, said second wall panel being bounded by a cut top edge; a lock flap articulated to said first wall panel along a flap fold line forming substantially a continuation of said second panel fold line, considering the blank in flat condition; said second wall panel having an internal cut in it through which the end portion of said lock flap is inserted, said internal out being of bent outline and defining an internal tongue in said second wall panel overlying the end portion of said lock flap to urge said lock flap flat against the outside of said second panel, said flap and said second panel being provided with an interlock including a first external cut extending into said lock flap from its cuttop edge at a second portion of said lock flap remote from said end portion which underlies said internal tongue, said second panel having a second external cut extending into it from its said cut top edge, each of said external cuts comprising an exterior portion adjacent the respective cut top edge and an interior portion remote from the top edge, the distance of the interior portion of the cut in the lock flap measured from the flap fold line being substantially equal to the distance of the interior portion of the cut in the second wall panel from the corner, the distance of the interior portions of the external cuts from the corner being less than the distance of any portion of said internal cut from the corner, the interior portions of both external cuts being in coincidence in the squared corner, the exterior portions of said external cuts being staggered and out of coincidence by reason of the first cut meeting the top edge of said flap at a point closer to said lock flap fold line than the distance from the corner to the 7 point of entry of said second cut into the top edge of the second wall panel, the top portion of the lock flap on the far side of the first cut, with respect to the corner, being flexible by a twisting force applied to said second panel and said lock flap adjacent said external cuts from a position overlying said second wall panel into a position underlying the near top portion of the second wall panel in the assembled corner in which position the interior portions of the two cuts are in edge-to-edge engagement, thereby locking the corner in erected condition, the said second portion of the lock flap overlying the said second wall panel on the near side of well as on the far side of the external cut, except for said top portion which underlies said second panel.

7. A corner construction for a folding box, particularly for a lined box in which a box liner blank overlies, and is attached to, the inside surface of the box blank,

3 the box" corner comprising, .a main panel; a first wall panel articulated to said main panel along a first panel fold line; 'a second wall panel articulated to said main 'panel along a second 'pauelfold line intersecting said first panel fold line at right angles;a lock'flap articulated to said first wall panel along a flap fold line' forming substantially a continuation of said second panel fold line, considering the blank in flat condition; said second wall panel having an internal cut in'it through which'a portion of said lock flap is inserted in a position in which the surface of the flap rests against the surface of said second panel, the internal cut lockingthe flap with said second wall panel against separation of theirlcontacti ng surfaces, the internal cut terminating at. a point substantially in coincidence with an outer edge of. the lock flap in corner forming position, thereby arresting the lock ,fiap against movement beyond the ,position in which the-corner is squared, said flap and said second panel being provided with an-interlock including a first external cut extending into said lock flap. from its top edge, said second panel having a second v external cut extending into it from its top edge, each ofgsaid external cuts comprising an exterior portion adjacent the respective top edge and an interior, portion remotefrom .the top edge, the distance'of the interiorlportion of the cut in the lock flap measured from the flap fold line being substantially equal to the distance of the interior portion of the cut in the second wall panel from the corner, whereby the interior portions of'both external cuts are in coincidence in the squared corner, the exterior portions of said external cuts being out of coincidence by reason of the first cut meeting the top edge of said flap at a point closer to said lock flap fold line than the distance from the corner to the point of entry of said second cut into the top edge of the second wall panel, the top portion of the lock flap onthe far side of the first cut, with respect to the corner, being flexible from 'a'position overlying said second wallpan'el'into a position underlying the near topqportion of the second. wall' panel in the assembled corner in which position the interior portions of the two cuts are in edge-to-edge engagement, thereby locking the corner in erected condition.

8. A' corner construction for a folding box comprising a box blank and a liner blank overlying, and attached to, the inside surfaceof the box blank, the box corner comprising. a main panel; a first wall panel articulated to said main panel along a first panel fold line; a second wall panel articulated to said main panel along a second panel fold line intersecting said first panel fold line at right angles; a corner flap articulated to said second panel along a corner flap fold line forming substantially a. continuation of said first panel fold line considering the blank in flat condition,the liner, being adhesively attached to said corner flap; a lock flap articulated'to said firstwall panel along a flap fold line forming substantially a continuation of said second panel fold line, considering the blank in flat condition, said second wall panel having an internal cut in it through which a portion of said lock flap is inserted in a position in which the surface of the flap rests against the surface of said second panel, the internal cut locking the flap with said second wall panel against separation of their contacting surfaces, said flap in said second panel beingprovided with. an interlock including a first external cut extending into said lock,

flap from its top edge, said second panel having a'second external cut extending into it from its top edge, each of said external cuts comprising anexterior portion adjacent the respective top edge and aninterior 'portion remote from the top 'edge, the distance of the interior portion in the lock 'fiap measured from the lock flap fold line being substantially equal 'to the 'distance of.

the interior portion of the cut in the second wall panel from the corner flap fold line, whereby the interior portions of both external cuts are in coincidence in the squared corner, the exterior portions of said external-- cuts being out of coincidence by reason of the first cut fere ce! Cited in the file of this patent meeting the top edge of the flap at a point closer to said lock flap fold line than the distance from the corner UNITED STATES PATENTS flap fold line to the point of entry of said second cut 472,797 McDonald i into the top edge of the second wall panel, the top 5 g f portion of the lock flap on the far side of the first cut, 1981836 f g 1934 with respect to the corner, being flexible from a position 2503798 Buttery 1950 flying Said wan Panel a under" 2 617 579 Buttery IIIIIIII: Nov: 11: 1952 lying the near top portion of the second wall panel in 2675164 Haas Apt .13, 1954 the assembled corner in which position the interior porlo 1 Helmick' Sept. 27, 1955 tions of the two cuts are in edge-to-edge engagement, FOREIGN PATENTS thereby locking the corner in erected condition.

282,239 Switzerland July 16, 1952 UNITED STATES PATENT OFFICE CERTIFICATE OF "CORRECTION Patent No. 2,837,261 June 3, 1958 Richard 0., Stenger It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column '7, line 70, for "of" read e as Signed and sealed this 4th day of November 1958.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Commissioner of Patents Attesting Officer 

